The invention relates to marine propulsion devices, and more particularly to marine propulsion device drive trains.
Prior marine propulsion devices include vertical drive shaft assemblies having an upper end fixedly connected to a bevel gear or to an engine crankshaft, and a lower end fixedly connected to a bevel gear. In some prior marine propulsion devices, the upper and lower ends of the vertical drive shaft assembly are fixedly connected to bevel gears by tight spline joints. Some prior vertical drive shaft assemblies include two or three drive shaft segments interconnected by spline-like joints.
In some prior marine propulsion devices, the axes of rotation of the upper and lower gears (at the opposite ends of the vertical drive shaft assembly) are or become misaligned so that undesirable bending and shearing stresses are imposed on the vertical drive shaft assembly. Such misalignment is especially common in marine propulsion devices having upper and lower gearcases, with the upper gear being mounted in the upper gearcase and the lower gear being mounted in the lower gearcase. Misalignment of the upper and lower gears results from imperfect connection of the two gearcases, or from the build-up of production tolerances.
Attention is directed to the following U.S. patents which disclose marine propulsion device vertical drive shaft assemblies:
______________________________________ Kucher 3,896,757 July 29, 1975 Barker 3,583,356 June 8, 1971 Wynne 3,376,842 April 9, 1968 Kiekhaefer 3,259,100 July 5, 1966 Ackerman 3,256,851 June 21, 1966 Shimanckas 3,183,880 May 18, 1965 Kiekhaefer 3,181,494 May 4, 1965 Shipley 3,138,010 June 23, 1964 Standal 3,051,120 Aug. 28, 1962 Tenney 3,025,822 March 20, 1962 Hansson 3,006,311 Oct. 31, 1961 Patty, Jr. 2,936,730 May 17, 1960 Krueger 2,917,019 Dec. 15, 1959 Bokowski 2,880,689 April 7, 1959 Bossen 2,384,436 Sept. 11, 1945 Johnson 1,824,213 Sept. 22, 1931 Evinrude 1,790,856 Feb. 3, 1931 Griffith 1,780,075 Oct. 28, 1930 ______________________________________